Immediate effect of bromocryptine on plasma hormone concentrations during early lactation in crossbred goats

Abstract

Six crossbred goats were administered 5 mg day −1 of bromocryptine intramuscularly for 5 consecutive days in early lactation of 15–20 days and repeated after a 13-day interval for another 5 days. Blood samples were collected before administration of bromocryptine (`0' time) and thereafter at 30, 60 and 90 min. Immediate effect of bromocryptine administration on circulatory levels of prolactin, growth hormone, cortisol, insulin, thyroxine and triiodothyronine was studied. It was found that plasma prolactin decreased within 30 min of bromocryptine administration in both periods of study. At `0' time of day 2 the levels of prolactin were higher than at 90 min of day 1 because in some of the goats the values tended to be high by then.The levels of growth hormone, cortisol, insulin, thyroxine and triiodothyronine were not suppressed by bromocryptine treatment.